A cutting element and methods of making same

ABSTRACT

A cutting element ( 30 ) includes a substrate ( 40 ) having a peripheral side edge, the peripheral side edge having an associated radius of curvature; and a body of superhard polycrystalline material bonded to the substrate along an interface, the body of superhard polycrystalline material ( 39 ) having a peripheral side edge and a longitudinal axis. The body of superhard polycrystalline material ( 39 ) has a working surface ( 54 ); and a plurality of spaced apart cutting edges extending to the working surface ( 54 ) through respective chamfer portions ( 62 ), the cutting edges ( 61, 76 ) being spaced around the working surface by a further region. The cutting edges ( 61, 76 ) have an associated radius of curvature, the radius of curvature of one or more of the cutting edges being less than the radius of curvature of the substrate. A method of making such a cutting element is also disclosed.

FIELD

This disclosure relates generally to a cutting element, for exampleformed of a super-hard polycrystalline construction that may be used,for example, as a cutting element for drilling in the oil and gasindustry or as an insert for machine tools, and to methods for makingthe same.

BACKGROUND

In various fields such as earth-boring, road milling, and mining toughmaterials such as rock, asphalt, or concrete are engaged and degradedusing cutting elements that are typically coupled to a movable body suchas a drill bit secured to a drill string to bring the cutting elementsinto contact with the material to be degraded as the body moves. Forexample, when exploring for or extracting subterranean oil, gas, orgeothermal energy deposits, a plurality of cutting elements aretypically secured to a drill bit attached to the end of a drill stringand as the drill bit is rotated, the cutting elements degrade asubterranean formation forming a wellbore, which allows the drill bit toadvance through the formation. In another example, when preparing anasphalt road for resurfacing, cutting elements are typically coupled totips of picks that may be connected to a rotatable drum. As the drum isrotated, the cutting elements degrade the asphalt leaving a surfaceready for application of a fresh layer.

The cutting elements used in such applications often include super-hardmaterials, such as polycrystalline diamond material, sintered to asubstrate material such as tungsten carbide, in a high-pressure,high-temperature environment. These cutting elements typically include acutting edge formed in the super-hard material designed to scrapeagainst and shear away a surface. While effective in cutting formationor other materials, such cutting elements may be susceptible tochipping, cracking, or partial fracturing when subjected to high forces.

In, for example, drilling operations, a cutting element, also termed aninsert, is subjected to heavy loads and high temperatures at variousstages of its useful life. In the early stages of drilling, when thesharp cutting edge of the insert contacts the subterranean formation, itis subjected to large contact pressures. This results in the possibilityof a number of fracture processes such as fatigue cracking beinginitiated. As the cutting edge of the insert wears, the contact pressuredecreases and is generally too low to cause high energy failures.However, this pressure can still propagate cracks initiated under highcontact pressures and may eventually result in spalling-type failures.In the drilling industry, PCD cutter performance is determined by acutter's ability to achieve high penetration rates in increasinglydemanding environments, and still retain a good condition post-drilling(enabling re-use if desired). In any drilling application, cutters maywear through a combination of smooth, abrasive type wear andspalling/chipping type wear. Whilst a smooth, abrasive wear mode isdesirable because it delivers maximum benefit from the highlywear-resistant PCD material, spalling or chipping type wear isunfavourable. Even fairly minimal fracture damage of this type can havea deleterious effect on both cutting life and performance.

Cutting efficiency may be rapidly reduced by spalling-type wear as therate of penetration of the drill bit into the formation is slowed. Oncechipping begins, the amount of damage to the diamond table continuallyincreases, as a result of the increased normal force required to achievea given depth of cut. Therefore, as cutter damage occurs and the rate ofpenetration of the drill bit decreases, the response of increasingweight on bit may quickly lead to further degradation and ultimatelycatastrophic failure of the chipped cutting element.

It has been appreciated that cutting elements and machine tool cuttinginserts having cutting surfaces with non-planar, shaped topographies ortopologies may be advantageous in various applications. In particular,the surface features and/or shape of the cutting surface may bebeneficial in use to divert, for example, chips from the working surfacebeing worked on by the cutter or machine tool, and/or in some instancesto act as a chip breaker, with a view to reducing the risk of chipping,or cracking, thereby extending the working life of the cutting element.

There is a need to provide super-hard inserts such as inserts forcutting or machine tools having effective performance and enhancedresistance to chipping or spalling.

SUMMARY

Viewed from a first aspect there is provided a cutting elementcomprising:

a substrate having a peripheral side edge, the peripheral side edgehaving an associated radius of curvature; and

a body of superhard polycrystalline material bonded to the substratealong an interface, the body of superhard polycrystalline materialhaving a peripheral side edge; wherein:

the body of superhard polycrystalline material comprises:

a working surface; and

a plurality of spaced apart cutting edges extending to the workingsurface through respective chamfer portions, the cutting edges beingspaced around the working surface; wherein

the cutting edges have an associate radius of curvature, the radius ofcurvature of one or more of the cutting edges being less than the radiusof curvature of the substrate.

Viewed from a second aspect there is provided a method of making thecutting element defined above comprising:

providing a mass of particles or grains of superhard material to form apre-sinter assembly; and

treating the pre-sinter assembly in the presence of a catalyst/solventmaterial for the superhard grains at an ultra-high pressure of around5.5 GPa or greater and a temperature at which the superhard material ismore thermodynamically stable than graphite to sinter together thegrains of superhard material to form the cutting element.

Viewed from a yet further aspect there is provided a drill bit or acomponent of a drill bit for boring into the earth, comprising one ormore of the above defined cutting elements.

In examples where the insert is used as a cutting element, for examplefor drilling in the oil and gas industry, the shape of the cuttingelement and any surface topography may be used to direct or divert therock or earth away from the drill bit to which the cutter is attached.Alternatively or additionally, for such uses or when used as an insertfor a machine tool for machining a work piece, the shape and surfacetopography may act as a chip breaker suitable for controlling aspects ofthe size and shape of chips formed in use.

BRIEF DESCRIPTION OF THE DRAWINGS

Various examples are now described with reference to the accompanyingdrawings in which:

FIG. 1 is a schematic drawing of a conventional PCD compact comprising aPCD structure bonded to a substrate;

FIG. 2 is a schematic drawing of the microstructure of a conventionalbody of PCD material;

FIG. 3 is a schematic drawing of a conventional PCD compact comprising aPCD structure bonded to a substrate having a chamfered peripheral edgeto act as a cutting edge;

FIG. 4 is a schematic perspective view from above of a cutting elementaccording to a first example;

FIG. 5 is a further schematic perspective view from above of the cuttingelement of FIG. 4;

FIG. 6 is a plan view of the cutting element of FIG. 4;

FIG. 7 is a schematic perspective view from above of a cutting elementaccording to a second example;

FIG. 8 is a plan view of the cutting element of FIG. 7;

FIG. 9 is a plot showing the results of a vertical borer test comparingan example cutting element with a conventional PCD cutter element; and

FIG. 10 is schematic perspective view from above of a cutting elementaccording to a further example.

DETAILED DESCRIPTION

Referring in general to the following description and accompanyingdrawings, various versions of the present disclosure are described andillustrated to show its structure and method of operation. Commonelements of the illustrated examples are designated by the samereference numerals.

As used herein, “drill bit” means and includes any type of bit or toolused for drilling during the formation or enlargement of a wellbore insubterranean formations and includes, for example, fixed cutter bits,rotary drill bits, percussion bits, core bits, eccentric bits, bi-centerbits, reamers, mills, drag bits, roller cone bits, hybrid bits and otherdrilling bits and tools known in the art.

As used herein, a “superhard material” is a material having a Vickershardness of at least about 28 GPa. Diamond and cubic boron nitride (cBN)material are examples of superhard materials.

As used herein, a “superhard construction” means a constructioncomprising a body of polycrystalline superhard material. In such aconstruction, a substrate may be attached thereto.

As used herein, polycrystalline diamond (PCD) is a type ofpolycrystalline superhard (PCS) material comprising a mass of diamondgrains, a substantial portion of which are directly inter-bonded witheach other and in which the content of diamond is at least about 80volume percent of the material. In one example of PCD material,interstices between the diamond grains may be at least partly filledwith a binder material comprising a catalyst for diamond. As usedherein, “interstices” or “interstitial regions” are regions between thediamond grains of PCD material. In examples of PCD material, some or allinterstices or interstitial regions may be substantially or partiallyfilled with a material other than diamond, or they may be substantiallyempty. PCD material may comprise at least a region from which catalystmaterial has been removed from the interstices, leaving interstitialvoids between the diamond grains.

Cutter elements for use in drill bits in the oil and gas industrytypically comprise a layer of polycrystalline diamond (PCD) bonded to acemented carbide substrate. PCD material is typically made by subjectingan aggregated mass of diamond particles or grains to an ultra-highpressure of greater than about 5 GPa, and temperature of at least about1200° C., typically about 1440° C., in the presence of a sintering aid,also referred to as a solvent-catalyst material for diamond.Solvent-catalyst materials for diamond are understood to be materialsthat are capable of promoting direct inter-growth of diamond grains at apressure and temperature condition at which diamond is thermodynamicallymore stable than graphite.

Examples of solvent-catalyst materials for diamond are cobalt, iron,nickel and certain alloys including alloys of any of these elements.

As used herein, PCBN (polycrystalline cubic boron nitride) materialrefers to a type of superhard material comprising grains of cubic boronnitride (cBN) dispersed within a matrix comprising metal or ceramic.

The term “substrate” as used herein means any substrate over which thesuperhard material layer is formed. For example, a “substrate” as usedherein may be a transition layer formed over another substrate.

The superhard construction shown in the figures may be suitable, forexample, for use as a cutter insert for a drill bit for boring into theearth. Such an earth-boring drill bit (not shown) includes a pluralityof cutting elements, and typically includes a bit body which may besecured to a shank by way of a threaded connection and/or a weldextending around the earth-boring drill bit on an exterior surfacethereof along an interface between the bit body and the shank. Aplurality of cutting elements are attached to a face of the bit body,one or more of which may comprise a cutting element as described hereinin further detail below.

FIGS. 1 and 2 show a conventional polycrystalline composite construction1, 1′ for use as a cutter insert for a drill bit (not shown) for boringinto the earth. The polycrystalline composite compact or construction 1,1′ comprises a body of polycrystalline super hard material 2, 2′integrally bonded at an interface 12 to a substrate 10. The super hardmaterial may be, for example, polycrystalline diamond (PCD) and thesuper hard particles or grains may be of natural or synthetic origin.

The substrate 10 may be formed of a hard material such as a cementedcarbide material and may be, for example, cemented tungsten carbide. Thebinder metal for such carbides suitable for forming the substrate 10 maybe, for example, nickel, cobalt, iron or an alloy containing one or moreof these metals. Typically, this binder will be present in an amount of10 to 20 mass %, but this may be as low as 6 mass % or less. Some of thebinder metal may infiltrate the body of polycrystalline super hardmaterial 2, 2′during formation of the compact 1, 1′.

As shown in FIG. 2, during formation of the polycrystalline compositeconstruction 1, 1′, the interstices 24 between the grains 22 of superhard material such as diamond grains in the case of PCD, may be at leastpartly filled with a non-super hard phase material. This non-super hardphase material, also known as a filler material may comprise residualcatalyst/binder material, for example cobalt, nickel or iron.

The polycrystalline composite construction 1, 1′ when used as a cuttingelement may be mounted in use in a bit body, such as a drag bit body(not shown).

The substrate 10 may be, for example, generally cylindrical having aperipheral surface 3, a peripheral top edge 8 and a distal free end.

The exposed surface of the super hard material 4 opposite the substrate10 forms or comprises a working surface which also acts as a rake facein use. In some conventional cutting elements such as that shown in FIG.3, a chamfer 28 typically extends between the working surface 4 and acutting edge 6, and at least a part of a flank or barrel 2 of thecutting element, the cutting edge 36 being defined by the edge of thechamfer 28 and the flank 2.

The working surface or “rake face” 4 of the polycrystalline compositeconstruction 1, 1′ is the surface or surfaces over which the chips ofmaterial being cut flow when the cutter is used to cut material from abody, the rake face 4 directing the flow of newly formed chips. Thisface 4 is commonly also referred to as the top face or working surfaceof the cutting element as the working surface 4 is the surface which,along with its edge 6, is intended to perform the cutting of a body inuse. It is understood that the term “cutting edge”, as used herein,refers to the actual cutting edge, defined functionally as above, at anyparticular stage or at more than one stage of the cutter wearprogression up to failure of the cutter, including but not limited tothe cutter in a substantially unworn or unused state.

As used herein, “chips” are the pieces of a body removed from the worksurface of the body being cut by the polycrystalline compositeconstruction 1, 1′ in use.

As used herein, the “flank” 2 of the cutter is the surface or surfacesof the cutter that passes over the surface produced on the body ofmaterial being cut by the cutter and is commonly referred to as the sideor barrel of the cutter. The flank 2 may provide a clearance from thebody and may comprise more than one flank face.

As used herein, a “wear scar” is a surface of a cutter formed in use bythe removal of a volume of cutter material due to wear of the cutter. Aflank face may comprise a wear scar. As a cutter wears in use, materialmay progressively be removed from proximate the cutting edge, therebycontinually redefining the position and shape of the cutting edge, rakeface and flank as the wear scar forms.

With reference to FIG. 3, the chamfer 28 is formed in the structureadjacent the cutting edge 6 and flank or barrel surface 2.

The rake face 4 is joined to the flank 2 by the chamfer 28 which extendsfrom the cutting edge 6 to the rake face 4, and lies in a plane at apredetermined angle to the plane perpendicular to the plane in which thelongitudinal axis of the cutter extends. In some examples, this chamferangle is up to around 45 degrees. The vertical height of the chamfer 28may be, for example, between 350 μm and 450 μm, such as around 400 μm.

The conventional cutting elements shown in FIG. 1 to 3 are typicallycylindrical in shape with a substantially planar cutting surface 4.

A cutting element 30 according to a first example is shown in FIGS. 4 to6 and comprises a body of polycrystalline super hard material 39integrally bonded at an interface 44 to a substrate 40. The super hardmaterial 39 may be, for example, polycrystalline diamond (PCD) and thesuper hard particles or grains may be of natural or synthetic origin.

The substrate 40 may be formed of a hard material such as a cementedcarbide material and may be, for example, cemented tungsten carbide,cemented tantalum carbide, cemented titanium carbide, cementedmolybdenum carbide or mixtures thereof. The binder metal for suchcarbides suitable for forming the substrate 40 may be, for example,nickel, cobalt, iron or an alloy containing one or more of these metals.Typically, this binder will be present in an amount of 10 to 20 mass %,but this may be as low as 6 mass % or less.

The substrate 40 may be, for example, generally cylindrical having aperipheral surface 33, a peripheral top edge 44 and a distal free end.

The body of superhard material 39 comprises a substantially cylindricalfirst region 42 bonded to the substrate 40 along the interface 44. Afurther region 46 extends therefrom to an exposed surface of the superhard material 34 opposite the substrate 40 which forms or comprises aworking surface, also termed a cutting face which also acts as a rakeface in use. This working surface has a central portion which issubstantially non-planar and may, in some examples, be concave, orconvex or have one or more regions that include both a concave and aconvex portion to form an undulating profile. The further region 46 hasan undulating peripheral surface which may assist in reducing drag onthe lateral surface of the cutting element in use and to improve cuttingefficiency by controlling chip flow over the external surfaces of thecutting element 30.

A plurality of curved cutting edges 41 are spaced from one anotheraround the working surface 34 and are formed by the bottom of arespective chamfer portion 37 extending between the working surface 34and further region 46 of the body of superhard material, the cuttingedges 41 being defined by the edge of the chamfer 37 and the top 38 ofthe further region 46.

1. The cutting edges 41 are spaced from each other by a respectiveinterconnecting region such that the cutting edges 41 form lobes 36extending from the working surface 34. A fillet portion 43 may extendfrom each interconnecting region terminating at or proximate theinterface 38 between the first region 42 and further region 46 of thebody of superhard material. In some examples, the fillet portion 43 andinterconnecting region between the plurality of spaced apart cuttingedges which extend between the working surface and the peripheral sideedge of the body of superhard polycrystalline material may be arcuate ina plane parallel to the longitudinal axis, for example concave.

In some examples, the central portion of the working surface 34comprises a concavity extending into the body of superhard material butterminating above the interface with the substrate 40.

In some examples, the depth of the first region 42 is between around 1mm to around 2 mm.

FIGS. 7, 8 and 10 show further example cutting elements 50, 70 whichdiffer from that shown in FIGS. 4 to 6 in that the radii of curvature ofthe cutting edges 61, 76 is smaller in the examples of FIGS. 7, 8 and 10than the first example of FIGS. 4 to 6.

In the example of FIGS. 7 and 8, the cutting element 50 comprises a bodyof polycrystalline super hard material 56 integrally bonded at aninterface 58 to a substrate 60. The super hard material 56 may be, forexample, polycrystalline diamond (PCD) and the super hard particles orgrains may be of natural or synthetic origin.

As in the first example, the substrate 60 may be formed of a hardmaterial such as a cemented carbide material and may be, for example,cemented tungsten carbide, cemented tantalum carbide, cemented titaniumcarbide, cemented molybdenum carbide or mixtures thereof. The bindermetal for such carbides suitable for forming the substrate 60 may be,for example, nickel, cobalt, iron or an alloy containing one or more ofthese metals. Typically, this binder will be present in an amount of 10to 20 mass %, but this may be as low as 6 mass % or less.

The substrate 60 may be, for example, generally cylindrical having aperipheral surface 55, a peripheral top edge 58 and a distal free end.

The body of superhard material 56 comprises a region 57 extending fromthe interface 58 with the substrate 60 to an exposed surface of thesuper hard material 54 opposite the substrate 60 which forms orcomprises a working surface, also termed a cutting face which also actsas a rake face in use. This working surface 54 has a central portionwhich is substantially non-planar and may, in some examples, be concave,or convex or have one or more regions that include both a concave and aconvex portion to form an undulating profile. The region 57 has anundulating peripheral surface which may assist in reducing drag on thelateral surface of the cutting element in use and to improve cuttingefficiency by controlling chip flow over the external surfaces of thecutting element 50.

A plurality of curved cutting edges 61 are spaced from one anotheraround the working surface 54 and are formed by the bottom of arespective chamfer portion 62 extending between the working surface 54and the region 57 of the body of superhard material 56, the cuttingedges 61 being defined by the edge of the chamfer 62 and the workingsurface 54.

2. The cutting edges 61 are spaced from each other by a respectiveinterconnecting region such that the cutting edges 61 form lobes 63extending from the working surface 54. A fillet portion 53 may extendfrom each interconnecting region terminating at or proximate theinterface 58 between the body of superhard material 56 and the substrate60. In some examples, the fillet portion 53 and interconnecting regionbetween the plurality of spaced apart cutting edges which extend betweenthe working surface and the peripheral side edge of the body ofsuperhard polycrystalline material may be arcuate in a plane parallel tothe longitudinal axis, for example concave.

In some examples, the central portion of the working surface 54comprises a concavity extending into the body of superhard material butterminating above the interface with the substrate 60.

In the example of FIG. 10, the cutting element 70 comprises a body ofpolycrystalline super hard material 75 integrally bonded at an interface73 to a substrate 71. The super hard material 75 may be, for example,polycrystalline diamond (PCD) and the super hard particles or grains maybe of natural or synthetic origin.

As in the first example, the substrate 71 may be formed of a hardmaterial such as a cemented carbide material and may be, for example,cemented tungsten carbide, cemented tantalum carbide, cemented titaniumcarbide, cemented molybdenum carbide or mixtures thereof. The bindermetal for such carbides suitable for forming the substrate 71 may be,for example, nickel, cobalt, iron or an alloy containing one or more ofthese metals. Typically, this binder will be present in an amount of 10to 20 mass %, but this may be as low as 6 mass % or less.

The substrate 71 may be, for example, generally cylindrical having aperipheral surface, a peripheral top edge and a distal free end.

The body of superhard material comprises a region 72 extending from theinterface 73 with the substrate 71 to an exposed surface of the superhard material 74 opposite the substrate 71 which forms or comprises aworking surface, also termed a cutting face which also acts as a rakeface in use. This working surface 74 has a central portion 77 which issubstantially non-planar and may, in some examples, be concave, orconvex or have one or more regions that include both a concave and aconvex portion to form an undulating profile.

A plurality of curved cutting edges 75 are spaced from one anotheraround the working surface 74 and are formed by the bottom of arespective chamfer portion 76 extending between the working surface 74and the region 72 of the body of superhard material, the cutting edges75 being defined by the edge of the chamfer 76 and the working surface74.

The cutting edges 75 are spaced from each other by a respectiveinterconnecting region 78 such that the cutting edges 75 form lobesextending from the working surface 74. The interconnecting region 78 mayhave an undulating peripheral surface which may assist in reducing dragon the lateral surface of the cutting element in use and to improvecutting efficiency by controlling chip flow over the external surfacesof the cutting element 70. In particular, the region 78 which extendsbetween the working surface 74 and the region 72 may be arcuate, forexample concave, in a plane parallel to the longitudinal axis.

In some examples, such as those shown in FIGS. 4 to 8 and 10, the depthalong a central longitudinal axis of the cutting element 30, 50, 70 ofthe concave central feature in the working surface 34, 54, 74 may be upto around 1mm. In examples, the central feature is convex, and theheight along a central longitudinal axis of the cutting element 30, 50,70 of the convex central feature protruding from the working surface 34,54, 74 may be up to around 1 mm.

In the examples, the radius of curvature of the cutting edges 41, 61, 75is less than the radius of curvature of the substrate 40, 60, 71 (and,in the example of FIGS. 4 to 6, the first region 42) which may improvethe rate of penetration of the cutting element in use. As anillustration, the radius of curvature of the cutting edges 41, 61, 75may, in some examples, be between around 2 mm to around 16 mm. By way offurther example, for a cutting element 30, 50, 70 in which substrate 40,60, 71 has a diameter of around 16 mm, the radius of curvature of one ormore of the cutting edges 41, 61, 75 may be between around 4 mm toaround 12 mm; for a cutting element in which the substrate 40, 60, 71has a diameter of around 19 mm, the radius of curvature of one or moreof the cutting edges 41, 61, 75 may be between around 6 mm to around 14mm; and for a cutting element in which the substrate 40, 60, 71 has adiameter of around 13 mm, the radius of curvature of one or more of thecutting edges 41, 61, 75 may be between around 3 mm to around 9 mm.

In some examples, the depth of the central recess in the working surface34, 54, 74 in a plane parallel to the longitudinal axis of the cuttingelement 30, 50, 70 measured from the highest point on the workingsurface 34, 54, 74 to the bottom of the recess is between around 0.5 mmto around 2.5 mm, and the distance along said axis from the bottom ofthe central recess to the interface 44, 58, 73 with the substrate 40,60, 71 is between around 1 to around 2 mm, and in some examples is atleast around 1.4 mm.

The wear resistance of the example cutting elements 30, 50, 70 weretested against conventional polycrystalline diamond cutting elementshaving the same average grain size of diamond grains as the super hardgrains in the example constructions 30, 50, 70 and sintered underpressure of around 6.8 GPa. The tests performed included vertical boringmill tests. The results are shown in FIG. 9 and provide an indication ofthe total wear scar area plotted against cutting length. It was seenthat the wear resistance of the example constructions was better thanthat of the conventional PCD cutting elements bonded to a WC substratein which the PCD layer had the same average grain size as the PCD layerof the examples and same PCD layer thickness. None of the cuttingelements had been subjected to an acid leaching treatment to removeresidual catalyst from the PCD regions.

An example method of preparing the cutting element of FIGS. 4 to 8 and10 is as follows. A pre-sinter mixture was prepared by combining a massof diamond particles with a non-diamond phase mixture designed to act asa solvent/catalyst for diamond, such as cobalt, and to form up to around20 wt % in the sintered product. The pre-sinter mixture was loaded intoa cup and placed in an HP/HT reaction cell assembly together with a massof carbide to form the substrate. The contents of the cell assembly weresubjected to HP/HT processing. The HP/HT processing conditions selectedwere sufficient to effect inter-crystalline bonding between adjacentgrains of diamond particles and the joining of sintered particles to thecemented metal carbide support to form a PCD construction comprising aPCD structure integrally formed on and bonded to the cemented tungstencarbide substrate. In one example, the processing conditions generallyinvolved the imposition for about 3 to 120 minutes of a temperature ofat least about 1200 degrees C. and a super high pressure of greater thanabout 5 GPa. In some examples, the pre-sinter assembly may be subjectedto a pressure of at least about 6 GPa, at least about 6.5 GPa, at leastabout 7 GPa or even at least about 7.5 GPa or more, at a temperature ofaround 1440 deg C.

In some examples, both the bodies of, for example, diamond and carbidematerial plus sintering aid/binder/catalyst are applied as powders andsintered simultaneously in a single UHP/HT process.

In another example, the substrate may be pre-sintered in a separateprocess before being bonded to the superhard material in the HP/HT pressduring sintering of the superhard polycrystalline material.

In some examples, the cemented carbide substrate 40, 60, 71 may beformed of tungsten carbide particles bonded together by the bindermaterial, the binder material comprising an alloy of any one or more ofCo, Ni and Cr. The tungsten carbide particles may form at least 70weight percent and at most 95 weight percent of the substrate.

After sintering, the PCD constructions 30, 50, 70 were subjected tofurther treatment to remove the canister material.

In some examples, the canister may be shaped to create one or more ofthe concave or convex central portion in the working surface 34, 54, 74the chamfers 37, 62, to create the cutting edges 41, 61, 75 and theundulating peripheral surface 46, 57, 78 of the body of superhardmaterial. In other examples, any one or more of the concave or convexcentral portion in the working surface 34, 54, 77 the chamfers 37, 62 tocreate the cutting edges 41, 61, 75 and the undulating peripheralsurface 46, 57, 78 may be created after sintering using additionalprocessing such as laser ablation, EDM machining another machiningprocess to shape the construction to the desired cutting element shapeand size. Additionally, laser ablation of different regions of thesuperhard material/working surface 34, 54, 74 may be used to createregions of different surface roughness, for example by ablating usingdifferent laser parameters. This may be used, as desired, to influencechip flow across the working surface 34, 54, 74 during the cuttingapplication.

The number, depth and dimensions of the lobes 36, 56, 75 and discretecutting edges 41, 61, 76 may be chosen to suit the desired application,and in some examples the cutting elements comprise three or more lobesto provide three or more cutting edges enabling the cutting element tobe spun to increase the working life of the cutting element and presenta new cutting edge to the surface to be cut.

In the examples where the body of superhard material comprises PCD, thePCD material may be, for example, formed of diamond grains that are ofnatural and/or synthetic origin.

The cutting elements 30, 50, 70 of the types shown in FIGS. 4 to 8 and10 may be provided along blades on the face of a drill bit body (notshown). The cutting elements may be secured to the bit body withinpockets therein using, for example a conventional brazing process.

In some examples, the example constructions may be subjected to an acidleaching treatment to remove the residual catalyst from interstitialspaces between the grains of superhard material.

In use, the cutting element 30, 50, 70 shears away the surface of theunderlying formation and wear scar forms progressively in the superhardmaterial in the region of the cutting edge 41, 61, 76. As used herein, a“wear scar” is a surface of the cutter formed in use by the removal of avolume of cutter material due to wear of the cutter. As a cutter wearsin use, material may progressively be removed from proximate the cuttingedge, thereby continually redefining the position and shape of thecutting edge, rake face and flank as the wear scar forms.

Whilst not wishing to be bound by a particular theory, the examplecutting elements are believed to assist in providing improved rockcutting efficiency over conventional PCD cutters, as the geometry of thecutting-edges 41, 61, 76 having a smaller radius of curvature than thesubstrate 40, 60, 70 and the undulating peripheral surface and theundulating working surface 34, 54, 74 is such that the wear scar areawill grow at a far slower rate than for a conventional cylindrical PCDcutter. This is believed to assist in maintaining a greater load at thecutter-rock contact point for a longer period, resulting in a slowerbuild up of thermal loading, both of which are believed to becontributors to more efficient rock cutting. Also, the undulatingworking surface 34, 54, 74 may assist in providing more efficientcrushing and removal of the rock cuttings and chips in application.

In some examples, the cutting elements may have a generally cylindricalshape. In other examples, the cutting elements be a different shape,such as conical, or ovoid.

In some examples, the body of PCD material may be formed as a standaloneobject, that is, a free-standing unbacked body of PCD material, and maybe attached to a substrate in a subsequent step.

In some examples, the cutting elements may comprise natural or syntheticdiamond material, or cBN material. Examples of diamond material includepolycrystalline diamond (PCD) material, thermally stable PCD material,crystalline diamond material, diamond material made by means of achemical vapour deposition (CVD) method or silicon carbide bondeddiamond. An example of cBN material is polycrystalline cubic boronnitride (PCBN).

It will therefore be seen that various versions of the presentdisclosure include cutting elements and methods of forming same forearth-boring drill bits which may enhance the working life of thecutting elements by one or more of improving the abrasion resistance,thermal stability, durability, sharpness of the cutting edge, spallresistance, and fracture/impact resistance, potentially by cutting therock more efficiently through the rock crushing action and control ofchip and drilling mud flow through the shapes/topography of the cuttingelements and may lead to improved drill bit stability of, for example,the earth-boring drill bit to which the cutting elements may be mounted.

Although the foregoing description contains many specifics, these arenot to be construed as limiting the scope of the present disclosure, butmerely as providing certain exemplary versions.

1. A cutting element comprising: a substrate having a peripheral sideedge, the peripheral side edge having an associated radius of curvature;and a body of superhard polycrystalline material bonded to the substratealong an interface, the body of superhard polycrystalline materialhaving a peripheral side edge and a longitudinal axis; wherein: the bodyof superhard polycrystalline material comprises: a working surface; anda plurality of spaced apart cutting edges extending to the workingsurface through respective chamfer portions, the cutting edges beingspaced around the working surface by a further region; wherein thecutting edges have an associated radius of curvature, the radius ofcurvature of one or more of the cutting edges being less than the radiusof curvature of the substrate.
 2. A cutting element according to claim1, further comprising a protrusion or recessed region extending from theworking surface about a central longitudinal axis of the cuttingelement.
 3. The cutting element of claim 1, wherein the body ofsuperhard polycrystalline material comprises any one or more ofpolycrystalline diamond, diamond-like carbon, or cubic boron nitride ofnatural and/or synthetic origin.
 4. The cutting element of claim 1,comprising three or more cutting edges.
 5. The cutting element of claim1 wherein the working surface comprises an undulating topology.
 6. Thecutting element of claim 1, wherein the working surface comprises arecessed region extending to a position between around 0.5 mm to around2 mm above the interface between the body of superhard polycrystallinematerial and the substrate.
 7. The cutting element of claim 1, whereinthe chamfers extend at an inclined angle to the plane along which thelongitudinal axis of the cutting element extends.
 8. The cutting elementof claim 1, wherein the body of superhard polycrystalline materialcomprises polycrystalline diamond material having inter-bonded diamondgrains with interstitial spaces between the inter-bonded diamond grains,at least a portion of the interstitial spaces being substantially freeof metal solvent catalyst material.
 9. The cutting element of claim 1,wherein the radius of curvature of one or more of the cutting edges isbetween around 2 mm to around 16 mm.
 10. (canceled)
 11. (canceled) 12.(canceled)
 13. The cutting element of claim 1, wherein the workingsurface has a central recess therein having a depth in a plane parallelto the longitudinal axis of the cutting element measured from thehighest point on the working surface to the bottom of the recess ofbetween around 0.5 mm to around 2.5 mm; and/or the distance along saidaxis from the bottom of the central recess to the interface with thesubstrate is between around 1 to around 2 mm.
 14. The cutting element ofclaim 1, wherein the further region between the plurality of spacedapart cutting edges extends between the working surface and theperipheral side edge of the body of superhard polycrystalline material,the further region being arcuate in a plane parallel to the longitudinalaxis.
 15. The cutting element of claim 14, wherein the further region isconcave in a plane parallel to the longitudinal axis.
 16. Anearth-boring tool, comprising: a body; and at least one cutting elementaccording to claim 1 attached to the body.
 17. A method of making thecutting element of claim 1 comprising: providing a mass of particles orgrains of superhard material to form a pre-sinter assembly; and treatingthe pre-sinter assembly in the presence of a catalyst/solvent materialfor the superhard grains at an ultra-high pressure of around 5.5 GPa orgreater and a temperature at which the superhard material is morethermodynamically stable than graphite to sinter together the grains ofsuperhard material to form the cutting element.
 18. A method accordingto claim 17, wherein the step of providing a mass of grains of superhardmaterial comprises providing a mass of diamond grains to form a body ofpolycrystalline diamond material.
 19. (canceled)
 20. (canceled)
 21. Amethod according to claim 17, wherein the step of treating thepre-sinter assembly comprises treating the pre-sinter assembly in acanister that is shaped to create any one or more of the plurality ofspaced apart cutting edges extending to the working surface throughrespective chamfer portions, the topology of the working surface, or thetopology of the peripheral side surface.
 22. A method according to claim17, further comprising processing the cutting element after the step oftreating the pre-sinter assembly to create any one or more of theplurality of spaced apart cutting edges extending to the working surfacethrough respective chamfer portions, the topology of the workingsurface, or the topology of the peripheral side surface, wherein thestep of processing comprises using any one or more of laser ablation orEDM machining.
 23. (canceled)
 24. (canceled)
 25. (canceled) 26.(canceled)
 27. A drill bit or a component therefor comprising thecutting element according to claim 1.